A fuel injection valve for an internal combustion engine as illustrated in FIGS. 7, 8 and 9 is conventionally known. This conventional fuel injection valve includes a thin fuel jet adjusting plate having orifices (nozzle holes), a valve body having fuel flow passages for allowing fuel to flow therethrough, and a valve seat portion for slidably guiding a valve body in axial directions. FIG. 7 is a partial sectional side view of the fuel jet adjusting plate, the valve body and the valve seat portion of the conventional fuel injection valve for an internal combustion engine. FIG. 8 illustrates only the fuel jet adjusting plate and the valve seat portion viewed as indicated by an arrow VII in FIG. 7. FIG. 9 is a sectional view taken along line IX--IX in FIG. 7. As illustrated in FIGS. 7, 8 and 9, the valve seat portion is denoted by reference character 101, the fuel flow passages by 102, guide portions by 103, a guide surface by 104, the fuel jet adjusting plate by 105, the orifices (nozzle holes) by 106, the valve body by 107, and sliding surfaces by 108. The valve seat portion 101 includes the guide surface 104 which slidably guides the valve body 107. In this case, the sliding surface 108 of the valve body 107 is closely fitted to the guide surface 104 of the valve seat portion 101. Thus, the valve body 7 can move in top-to-bottom directions in FIG. 7 and assume either an open position or a closed position. Furthermore, the valve body 107 has the fuel flow passages 102 formed among the respective sliding surfaces 108. Thus, while the valve body 107 is securely guided with its sliding surfaces 108 closely fitted to the guide surface 104 of the valve seat portion 101, fuel can flow through the fuel flow passages 102 from top to bottom in FIG. 7. Thus, when the valve body 107 assumes the open position, fuel flowing through the fuel flow passages 102 is injected from the orifices 106 formed in the fuel jet adjusting plate 105. This type of fuel injection valve for an internal combustion engine is disclosed, for instance, in Japanese Patent Application Laid-Open No. HEI 7-127550.
In the case of the aforementioned fuel injection valve, however, the guide surface 104 and the sliding surfaces 108 allow the valve body 107 to slide relative to the valve seat portion 101. Thereby, the valve body 107 may not only move relative to the valve seat portion 101 in top-to-bottom directions in FIG. 7 but may also rotate circumferentially relative to the valve seat portion 101 (as indicated by an arrow A in FIG. 9). If the valve body 107 rotates relative to the valve seat portion 101, the fuel flow passages 102 attached to the valve body 107 also rotate circumferentially relative to the orifices 106 formed in the fuel jet adjusting plate 105 attached to the valve seat portion 101. This change in relative location between the fuel flow passages 102 and the orifices 106 causes alterations in pressures applied to fuel flowing through the respective orifices 6, flow rates of the fuel injected therefrom and the state of atomization of the fuel thus injected. As a result, the performance of an internal combustion engine on which the fuel injection valve is mounted is adversely affected.
In order to solve the aforementioned problems, according to another known fuel injection valve for an internal combustion engine, it is not a valve body but a valve seat portion that is equipped with fuel flow passages. FIG. 10 is a top view illustrating only a fuel jet adjusting plate and the valve seat portion of this known fuel injection valve having a valve seat portion equipped with fuel flow passages. FIG. 11 is a sectional view of the fuel injection valve taken along line XI--XI in FIG. 10, with a valve body mounted on the fuel injection valve. Referring to FIGS. 10 and 11, the valve seat portion is denoted by reference character 201, the fuel flow passages by 202, a guide portion by 203, a guide surface by 204, the fuel jet adjusting plate by 205, orifices (nozzle holes) by 206, the valve body by 207, and a sliding surface by 208. The fuel injection valve as illustrated in FIGS. 10 and 11 is different from the aforementioned fuel injection valve in that it is not the valve body 207 but the valve seat portion 201 that is equipped with the fuel flow passages 202. Thus, even if the valve body 207 rotates circumferentially relative to the valve seat portion 201, the orifices 206 do not rotate relative to the fuel flow passages. Thus, rotation of the valve body 207 does not cause any alteration in the pressure applied to fuel flowing through the respective orifices 206, flow rates of the fuel injected therefrom, and a state of atomization of the fuel thus injected. As a result, the performance of an internal combustion engine on which the fuel injection valve is mounted is not adversely affected.
Although the fuel flow passages 202 do not move relative to the orifices 206 in the aforementioned fuel injection valve, a relationship between the fuel flow passages 202 and the orifices 206 such as circumferential location of the orifices 206 relative to the fuel flow passages 202 and the number of the orifices 206 is not determined to obtain optimal atomization of injected fuel. For example, the pressure applied to the fuel flowing downstream of the fuel flow passages 202 is higher than that applied to the fuel flowing downstream of the guide portions 3. Thus, in the case where the orifices 206 located downstream of the fuel flow passages 202 and the orifices 206 located downstream of the guide portions 203 are arranged along the same circle, there is a difference in the state of atomization between the fuel injected from the orifices 206 located downstream of the fuel flow passages 202 and the fuel injected from the orifices 206 located downstream of the guide portions 203. Therefore, the state of atomization of fuel injected from the fuel injection valve depends on how the fuel injection valve is mounted on the internal combustion engine and depends more particularly on a circumferential rotation of the fuel injection valve. Nevertheless, the aforementioned fuel injection valve does not take this into account. In other words, since this fuel injection valve does not consider respective circumferential locations of the orifices 206 relative to the fuel flow passages 202 and the guide portions 203, the number of orifices 206 and so forth, a difference arises between the state of atomization in the respective orifices 206. In the aforementioned fuel injection valve, the respective orifices 206 are not arranged such that the fuel injected from the fuel injection valve is uniformly atomized. Hence, the fuel injected from the fuel injection valve is not uniformly atomized around a circumference thereof. Consequently, the state of atomization of injected fuel is not optimized.